Lubricant



Patented May 16, 1939 James H. Werntl, Wilmington, Del., assignor to V E. I. du Pont de Nemours '8; Company, Wilmington, Del., a corporation of Delaware Serial N0. 18,201

No Drawing. Application Aprilzi, 1938,

This invention relates to lubricants and particu'iarly to lubricants providing thin film lubricatron.

The advantages of a high pressure lubricant become apparent when the present trend in 'design of automotive and other machine parts, and the increased strength of metal parts, due to the use of alloy steels, is considered. The pressures ordinarily found in well lubricated journal bearl0 1188 do not exceed '2,000lbs./sq. in. and, for conditionssuch as this, a film of heavy oil can be expected to remain between the rubbing surfaces. when gears are considered, where the contact between surfaces is of very small width, the bearing pressures often reach values as high as 25,000

lbs. sq. in. Under such extreme pressure, it is u kely that any oil or grease can be obtained which will be viscous enough to prevent metallic contact. The result of the'lack of a'lubricating 2o film between the rubbing surfaces results'inscoring and scuffing of the gears,

Failure to maintain lubricant on idle bearing surfaces is now well recognizedas the cause of 70% to 80% of the wear occurring on cylinder walls of automotive'and other internal combustion engines. When an engine is stopped, the oil film on the vertical surfaces soon drains off. and, when the machine is again started up, I an appreciable time elapses before the circulation provides 011 for the formation of new lubricant films. An assistant which, when added to the motor oil, will prevent the separation of the oil film from the metal should prevent a large part of the wear now occurring.

Prior to this invention various assistants have been added to oils to improve their lubricating properties. Among such assisting materials which have been used are sulfur, sulfur chloride, sulfuriz ed oil or oil containing naturally occurring sulfur, various heavy metal soaps and alu.-'

minum soaps,castor oil and, recently aliphatic and aromatic halides. While some of these as sistants, such as the sulfur and the organic halides improve the lubricating properties of the oil to a great extent, they have not proved to be satisfactory for use for the reason that they are corrosive or give rise tov corrosive agents by bydrolysis or oxidation. Also, this corrosive'action is greatly intensified by the presence of small amounts of water. Some of the alkyl halides are volatile and, hence, are soon lost. Other assistants such as the alkali and heavy metal soaps have proved to be of little value in improving the lubricating properties of the oils.

An object of this invention is to provide meteri'alsf which, when brought intccontact with metal bearing surfaces, will form a lubricating film between such bearing surfaces, which lubri-' cating film will adhere to the metal surfaces and resist high pressures; A further object of.this s invention is to provide materials which, when added to lubricating media, improve their properties, particularly their adhesiveness and resistance to high pressure. A still further object is to provide a method for retarding the wear-- 10' ing, scuffing and seizing of bearing surfaces, adapted to operate at high bearing pressures, by contacting such surfaces with materials which will form adherent films on such bearing surfaces,

which films will not break down under high bear .iii

ing pressures. Other objects are to provide new compositions of matter and to advance the. art.-

'Still other objects will appear hereinafter.

- These objects may be accomplished in accordance with my invention which comprises maingo taining between relatively moving metallic bearing surfaces a film of a lubricating medium and at the same time chemically acting upon such surfaces by means of aliphatic acid esters of (ii-- basic organic acids in which the aliphatic radical g5 contains at least 6 carbon atoms or their amine salts. When such lubricants are brought into contact with metal bearing surfaces, the esters appear to react chemically with the metal thereof to form a non-corrosive lubricating film which so 7 will retard the wear of the bearing surfaces, will withstand high bearing pressures and willprevent metallic contact of the bearing surfacesunder high bearing pressures. The films have exceptional lubricating properties at all-pressures but 35 are particularly valuable at high bearing pressures and at high rubbing speeds. Such films will not be washed from the bearing surfaces by water, oil or organic solvents such as gasoline, naphtha and the like.

Preferably,.the lubricating medium will be a hydrocarbon oil or grease. However, other oils or greases such as the animal and vegetable fats and oils maybe employed. Also, preferably the esters of my invention will consist of the ele- 4s ments carbon, hydrogen and oxygen.

I-preferably employ the esters oi the dibasic acids in which the carboxyl groups are separated by atleast two intervening carbon atoms. Among the compounds which I have found-to be particuso larly effective for my purpose are the acid esters of citric, maleic, succinic and phthalic acids. Representative compounds are:

Octyl acid phthalate; cetyl acid phthaiate;

cetyl acid citrate; 9,10-octadecenyl acid citrate; 55 v parts of carbon alcohol, 57 parts of 12 carboni' alcohol and 22 parts 14 carbon alcohol. This mixture is kn'own to the trade as Lorol alcohol. (2) This is a mixture of esters prepared from the mixture of alcohols obtained by the carbox ylic reduction of a mixture of naphthenlc acids from petroleum. x The term bearing surfaces as employed here--. in and in the claims will be understood to mean surfaces which mutually carry a load and ;move relatively to each other.

The addition of as small an amount as 0.05%

and'the advantageous results tobe obtained of ester to an oil will have a noticeable effect.

- However, for practical purposes, it will generally 7 at this load.

about 125 lbs.. The machine provides for beam loadings up to weights which corresponds to a pressure of 20,000 lbs/sq. in. on the full projected area of the drill rod. The bearing surface of the bushing is cut to a diameter 0.007 inch larger than the drill rod so that, before any wear occurs, the actual bearing surface is a line. As wear occurs, the bearing surface widens but seldom covers the bushing. After a test, the width of the bearing scar can, be measured and an approximate value for the actual bearing pressure ob- ;tained. The values given in the following table represent the calculated actual bearing pressures which were reached in the test without failure of I the film. These values represent film strength or film resistance.

When subjected to the above test, a good grade of paraffin oil will withstand a pressure of only 3,000 to 6,000 lbs/sq. in. when an 011 containing Y sulfur is tested by the same method, such oil will show a film strength of about 20,000 lbs/sq. in. and will give a torque reading of over 4.0 lbs. ft.

In order to more clearly illustrate my invention thereby the results be found desirable to use from about 0.5 to about lowing table.

Allmen test malty Wt. No. Compound mt Oil medmm 1mm mam Y mu atmnx. load i000! lb. ft.

Nona SAE. 6 0.6

Octyl acid phthalate ,1 y do 74 3.3

Cotyl acid phthalate"--. 2 --...-d0 13 1.0 Oetyl acid citrate 2 31 v. 1.5

0 lo-octadeoenyl acid citn 2 l3 7 ,l. 4

Dodeoyl acid suzxinate 2 42 1. 7

Dodecyl acid maleate. 1 as 1, g

Dodecyl acid phthalste-. 1 42 1.4

"LoroP acid In 1 4s a 1 Octyl acid pbtbalate 1 Castor oil-.- 34 2.0

Ar rid phtlmlate of alcohols from petro- 2 SAE. 30 38 2. 5

enm.

Lore acid phthalate 2 .do 18 1.3 12, Naphthenyl acid phtbalete 2 ---..do- 24 2.8

I The oil medium uged in the above mixtures was an ebsentially naphtbenic lubricating oil of characteristics corresponding to SAE.

example, it is generally advisable to use higher concentrations of assistant in gear oils than would be employed in lubrication of internal combustion engin s. Concentrations up to 20% might be advantageously employed in" special cases. the amount added to the oil or other lubricating medium will be largelyfdependant upon the machinery in which it is applied and the areaof the metal surfaces with which it will be brought into contact.

The method of testing my compounds was that devised by J. O. Allmen .(Oil and Gas Journal, 30, 109, 1931). This method consists of running a V4 diameter drill rod between two halves of a split bushing which is maintained stationary. The load on the bushing is controllable and provision is made for measuring the torque developed by the friction of the lubricant film. A hydraulic system for increasing the loading on the bushing untilthc oil film breaks and the metal seizes is provided. The rubbing speed is about feet per minute and the method of loading is gradual, one weight being added to the loading lever each ten seconds; Each weight added to the loading lever increases the pressure'on' the bushing by The above tests. merelyillustrate' the results obtained with afew of the'compounds of my invention. Other compounds coming within my invention may be prepared from other aliphatic 50- -alcohols of 6 or more carbon atoms such as hexyl, I

cyclo-hexyl, decyl, hexadecyl, myric'yl, tetradecyl,

dodecyL'octa-decyl, linoleyl'and like long chain alcohols or mixtures of two or more of them or the primary alcohols obtained. by the oxidation of petroleum or alcohols obtained by the reduction of the acids. obtained from the petroleum orfrom' theioxidation of petroleum. Likewise the higher primary alcohols of 6 or more carbon:

atoms obtalned'by the hydrogenation of carbon atoms in the synthesis 'of methanol may be employed to prepare the esters of .my invention.v

Also, one'may employ esters of other'acids such as: Mono-methyl succinic; dimethyl succinic;

trl-methyl succinic; phenyl succinic; phenyl maleic; glutaric; adipic; suberic; fumaric; cltra- 'will be employed. In preparing such mixture of esters, mixtures of alcohols-may be reacted with an acid, as in the "Lorol acid maleate, Lorol .acid phthalate and naphthenyl acid phthalate.

oils and; greases. For example the oil can be heated until fluid enough to permit easy stirring liquids other than oils and greases renders them when theassistant maybe added. Agitati'on is then continued until the assistant hasdissolved at which time the mixture may be cooled.

The compounds of my invention, when brought into contact with the metallic bearing surfaces,

apparently react chemically therewith to form a iilm which is firmly-adherent to the metal and at the same time presents a surface to the main body of oil with which the oil is compatible; This results in the formation of a mechanicailyresistant surface on the bearing and at the sametime provides a bonding layer between the bearing and the oil, causing the oil and grease to adhere more firmly to the bearing surfaces. This is a particularly desirable and advantageous characteristic of my compounds particularly adapting them for use where the .bearing surfaces are vertical and an ordinary oil tends'to drain there? from, as in the cylindersof internal combustion engines. My compounds do not induce rusting and cause little or no corrosion on most metals,

when admixed with oils in contact with such metals.

The fact that my compounds retain their extreme pressure lubricating characteristics in particularly adapted for use as cutting oils, particularly in water emulsion. My compounds may be employed in other liquids than those mentioned in the examples. For instance, they may be em-.. ployed in benzene, gasoline, diphenyl, diphenyl oxide and any other liquid which isnon-corrosi've to metal and in which the compounds may be dissolved, dispersed or emulsified.

The use of cutting oils in machining operations is well known. The cutting fluid has two functhe friction between the cutting tool and the work,

and the second to provide a means for cooling the work.

The general practice is to use either an oil or a dispersion of oil in water. The oils used vary considerably depending on the particular operation and may vary from a light mineral oil to a Turkey red oil type. Recently the practice of.

adding sulfur or sulfur compounds has become common.

Die shaping of sheet metals and drawing ofsheets, wires and tubes has also recently been improved by the use of a lubricant between the contacting surfaces. v Cutting oils are now generally made up by compounding about 30 parts of lard oil, one to five parts of sulfur, two to ten parts of a petroleum or dispersed in water which improves its cooling properties.

The lard oil,'of course, breaks down under the high temperature conditions of use resulting in 4 at very low concentrations in'oilandcan be used on bearing lubrication'should also result from v portant results of their use.

, ,pounds referred to in this application isbelieved;

I and variations may be made therein without de- -ited solely by the appended claims construed as bricatin oil or ease containing small am tions; the firsttoprovide a lubricant to reduce 8 gr cunt in which the carboxyl groups are separated by bric'ating oil or grease containing a small amount 0 acid in which the carboxyl groups are separated 6 carbon atoms.-

. 3 the formation oidisagrceably odorcus materials. The presence or sulfur, as in motor and gear lubricants, is a possible sourceof corrosive material necessitating the careful washing of machined parts before use. These oils have also given con- A siderable trouble from infection of the workmen which is only partially eliminated by the incorporation of a bactericide in the-oil.

during all machining operations are obviously- I very high as they result in deformation of the metal. This is, therefore another problem of "v extreme pressure-lubrication. r

My compounds maybe usedin water, oil or other's'uitable media as cutting oil compositions with the attending elimination oi the odors and corrosiveness which are objectionable properties of most priorcutting oils. They will be effective in-water directly without the use ofan'cii medillm. 4 I v I Other improvements similar to those observed" such use. Decreased friction, safetyfrom cor rosion, and improved quality of the work are im- -80 The compounds oi my invention are in general well known and the methods for makingthem are also well known and described in the literature. Accordingly, a detailed description of the methods to be employed for making the comto be unnecessary. 4

While I have disclosed specific embodiments of my invention, it. will bereadily apparent to those skilled in the art that many modifications parting from the spirit of my invention. Accordingly, the scope of my invention is to be limbroadly as is permissible in view of the prior art.

I claim: 1. A high pressure lubricant comprising. a luof an aliphatic acid-ester of a dibasic organic acid, the aliphatic radical containing at least 6 carbon atoms.

2. A high pressure lubricant comprising a lubricating oil or grease containing a small amount of an allqrl acid-ester of a dibasic organic acid at least 2 intervening carbon atoms, the alkyl radical containing at least 6 carbon atoms.

3. A high pressure lubricant comprising a luof an aliphatic acid-ester of a dibasic organic by at least 2 intervening carbon atoms, the aliphatic radical containing at least 6 carbon atoms, said ester consisting of the elements carbon,- hydrogen and oxygen. I r

4. A high pressure lubricant comprising a hydrocarbon lubricating oil' or grease containing a small amount of an aliphatic acid-ester of a dibasic organic acid-in which the carboxyl groups are separated by at least 2 intervening carbon atoms, the aliphatic radical containing at least 5. A high pressure lubricant comprising a hydrocarbon lubricating oil or grease containing a small amount of an' alkyl acid ester of-a dibasic organic, acid in which the carboxyl groups are separated by at least 2 intervening carbon atoms, the alkyl radical containing at least 6 carbon atoms. we

6. A high pressure lubricant comprising a hydrocarbon lubricating oil or grease containing a small amount of an aliphatic acid-ester of a di-- basic organic acid in which. the carboxyl groups are separated by at least 2 intervening carbon atmm, the aliphatic radical containing at least 6 carbon atoms, said ester consisting of the ele--.

ments carbon,'hydrogen and oxygen. 7. A lilbrlcantfor internal combustion engines consisting of a lubricating oil and a small amount.

of an acid-ester derived from an 'organic acid containing at least 2 carboxyl groups separated by at least 2 intervening carbon atoms and an aliphatic alcohol. conta' ing at least 6 carbon atoms.

8. A high pressure lubricant comprising a lubricating oil or grease containing a small amount of an alkyl acid-ester o1 phthalic acid, the allcvl radical containing at least 6 carbon atoms.

9. A high pressure lubricant-comprisinga lubricating oil or grease containing a small amount of octyl acid phthalate. y

10. A high pressure lubricant comprising a. lubricating oil or grease containing a small amount ofnaphthenyl acid phthalate.

11. A high pressure lubricant comprising a lue bricating oil or grease containing a small amount of an alkyl acid-ester of maleic acid, the alkyl radical containing at least 6 carbon atoms.

* 12.. A high pressure lubricant comprising a lubricating oil or grease containing a small amount 

